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About 5 years ago, I discovered an aggregation of Andrenid bees nesting on the north slope of the Amphibian Pond. At that time they were in one location only. The next year I went back to the pond in early spring, hoping to find them. It wasn’t until late April that they appeared, in the same location, at the time a nearby willow was in flower. Eventually, I discovered that they were Andrena dunningi, a species known to time its emergence to coincide with the flowering of willow trees.

Andrenid bee. These bees were very active in early afternoon under a warm, sunny sky. I would guesstimate about 30-40 were seen, fewer than the number of nest holes.

Over the next few years, I found them mostly in the initial location, but in 2007, I also found some nesting in another section of the north slope, where an abundance of non-native plants, mostly mustards and Chenopodium species, were growing (for that one year). The nesting, of course, took place before these plants had grown to full height.

This year, 2011, the bees were first noticed in late April, and, interestingly, I saw they had spread from their original site to the upper section of the track around the pond (not the Bill Holland Trail, but the “informal” track that was created when the bridge was closed last year), and to the west side of this track. I counted about 30 entrance holes at that point.

Constant foot traffic on the track meant that the burrows were continually being closed over, although new holes appeared regularly.

Andrenids prefer areas of bare soil with scattered vegetation, such as sparsely growing grass, and show a distinct preference for the tops of slopes. Their burrows are about 4-6 inches in length, as best as I can determine, so we don’t want to plant species with deep spreading roots that might prevent them from burrowing. Reading I have done since last week indicates that they will nest under exposed tree roots, but they are much happier with bare soil.

Some of the plants we have considered for this location (and we are not restricting the list to native only) include clover, grasses and sedges that form clumps (such as poverty oat grass and peduncled sedge), and possibly vines that will grow down the slope such as wild grape or virginia creeper.

Freshly dug nest site: you can see the mound of soil around the hole.

Andrenid nest entrance. Freshly dug holes often have a mound of soil around them (see photo above), but rain washes this away. Many of the nest holes are not apparent at first, especially if not surrounded by a mound of soil. They are also very small, approx. 1/4 inch or less.

NOTE: As of May 2017, we have found at least 7 species of Andrenid bees at the FWG: Andrena cressonii, A. dunningi, A. miserabilis, A. nasonii, A rufosignata, A. vicina, and A. wilkella (the last one is the only non-native). In addition to this location next to the pond, we’ve also seen them in the Old Woodlot.

This is a simple overview of various types of accommodations for bees. I won’t be providing instructions for building bee boxes, but I do provide a reference below for the best all-round source for creating different types of bee houses.

Much media attention has been given to declining honeybees (Apis mellifera), but less well-known is the decline in many native bee species, such as bumble bees (Bombus) and others. Our native bees are facing habitat loss, pesticide contamination, disease, and who knows how many other problems. Studies are ongoing with more research devoted to this issue.

The good news is that people are becoming more aware of bees as beneficial. I spoke with a pest control official recently who said that although he still gets calls from people worried about bees, such calls are fewer than in the past. The ongoing media attention about disappearing honeybees and subsequent attention paid to bees in general, and their importance to pollination, has moved this group of insects into a more benign category.

One indication of the changing attitude is the recent interest in placing bee boxes (bee nest sites) in gardens. Although I am happy about this trend, there is also a downside. Buyers are not usually told that if they want to help bees, nectar rich plants must be available or bees won’t be interested. The importance of hygiene in bee boxes is rarely discussed either. Unfortunately, some commercially produced bee boxes are more concerned with making cute ornamental art for the garden than with the requirements of bees.

Many of our native bees are ground nesters and won’t use bee boxes. This brings up a whole different issue, which I’ll leave for another time, as this article is looking only at tunnel-nesting bees, the ones most likely to use bee boxes.

The natural nesting sites of these bees is the hollow stems of plants, such as wild raspberries, or holes in standing dead trees (snags). When we build bee boxes for them, we are emulating their natural nest sites, much as we do for cavity nesting birds when we install nest boxes.

The most common tunnel-nesting bees we see around the Ottawa are leaf-cutter bees and mason bees (both in the Megachilidae family). These are the ones that will be most attracted to bee boxes. Bumble bees may also be attracted to man-made nest sites. At the Fletcher Wildlife Garden (FWG), a newly installed bee box in summer 2009, attracted leafcutter bees (Megachile) within days. In 2012, scientists from Agriculture and Agri-Food Canada (AAFC) placed a number of bee boxes as well as bee bundles, around the garden in a variety of sites, and these too were very well-used, particularly the nest boxes.

There are innumerable ways to provide nesting sites for these bees, the simplest being to leave snags standing, and to grow plants that bees would use in the wild for nesting. Creating artificial nesting sites is the other option, and ways and means are varied and many.

First and always, when making any bee structure, think of hygiene, as parasites and disease are a serious problem for bees. With simple bee blocks, essentially a wooden cube with holes in it, there are two options: you can replace them every year or you can use removable cylinders in each hole. These can be straws or rolled tubes of paper, which can be discarded when the bees have finished nesting. The bee block can then be disinfected, instructions for which are given in the native pollinator book listed in references below.

Bee blocks work best if they have holes of varying diameters (to accommodate different bee species) and of sufficient depth to allow bees a long tunnel to work in. Some people suggest drilling the holes slightly upward to prevent rain from getting in. Logs with drilled holes can also be used for this same purpose. Old, weathered logs are best as they emulate the snags that bees would naturally use. At the FWG, I’ve noticed bees making nests in some of our old well-worn wooden posts (used for habitat signs) and the split-rail fences.

Other types of simple nest accommodations include bee bundles, which can be made from lengths of hollow stems, such as bamboo, phragmites (abundant in the region, although very invasive so make sure you don’t distribute the seedheads elsewhere), cup-plants. These are best if situated within some sort of cover (large black soft plastic plant pots were used by scientists who set up bee bundles at the FWG in 2012) to protect them from rain and located in a sheltered site. At the FWG, I’ve noticed mason bees checking out plants for nest sites, and they also used the AAFC bee boxes.

Bumble bees frequently nest in the ground, but they will also nest in piles of stones, brushpiles, under decks, and even in bird nest boxes (which I’ve seen several times at the FWG). I’ve also seen them nesting in the foundation of my house and in sheds. In other words, while their sites are varied, what they are seeking is a warm, dry, sheltered cavity.

Finally, some very creative ideas for creating “condos” or “hotels” for bees (and other insects too) come via the Pollinator listserv. These examples show how bee and insect condos can be constructed fairly simply, using found objects, such as plant stems, bricks, logs, etc. Ingenious designs from across Europe are shown, ranging from small and simple to quite large and more elaborate, all of which can be used and adapted for our area. General information about cleaning out bee blocks, and maintaining sites is given, as well as tidbits of other interesting information. Some of the photos show carefully constructed structures that will hold about 8 or 9 separate bee boxes. Others are created with boards or pallets, separated by bricks, and stuffed with a variety of material that will attract not only bees but other insects such as ladybeetles. The site is fun to peruse and is sure to generate a desire to emulate at least one of the structures. At the FWG we are already planning to create several and will be keeping an eye on them throughout the summer to see who uses them.

References:***Attracting Native Pollinators. Protecting North America’s Bees and Butterflies. 2011. By the Xerces Society. Storey Publishing. I can’t say enough good things about this marvellous book. It provides excellent information, complete with photos, of different types of bee structures, good instructions for how and when to install, how to keep nest boxes and bundles clean, and much more. Buy it!!! It is the best source around; you need no others!

NAPPC Pollinator listserv: pollinator.org/nappc/listservrules.htm Provides a variety of topical and worthwhile information with much current information about bees and their conservation and efforts to protect them.

Pollinator Partnership (NAPPC): pollinator.org/index.html Provides information about all pollinators, with an emphasis on bees.

Xerces Society: www.xerces.org/ One of the best all-round websites dedicated to bees and all pollinators, with a wealth of good, trustworthy information. Check under: www.xerces.org/fact-sheets/ for information on bee boxes.

More references for building bee boxes will be added when I find ones that are suitable.